In diseases and disorders such as hepatic cirrhosis, interstitial pulmonary disease, chronic renal failure (or disease resulting in chronic renal failure), hyperplasia scar after inflammation, postoperative scars or burn scars, scleroderma, arteriosclerosis, hypertension and the like, excessive accumulation of an extracellular matrix, a representative of which is collagen, causes fibrosis and sclerosis of tissues, resulting in decreased functions, cicatrization and the like in the organs or tissues. Such excessive accumulation of an extracellular matrix is induced by increased production of collagen due to a breakdown of balance between biosynthesis and degradation of collagen and the like. In fact, it has been observed that expression of a collagen gene, in particular, a Type I collagen gene has been increased in a fibrotic tissue [e.g. J. Invest. Dermatol., 94, 365, (1990) and Proc. Natl. Acad. Sci. USA, 88, 6642, (1991)]. It has been also observed that the amount of TGF-β, which is a cytokine, has been increased in a fibrotic tissue [e.g. J. Invest. Dermatol., 94, 365, (1990) and Proc. Natl. Acad. Sci. USA, 88, 6642, (1991)]. It has been shown that TGF-β has increased expression of a Type I collagen gene and been involved in increased production of collagen and, consequently, fibrosis of a tissue [e.g. Lab. Invest., 63, 171, (1990) and J. Invest. Dermatol., 94, 365, (1990)]. It has been also shown that by administering an anti-TGF-β antibody or a soluble anti-TGF-β receptor to a model animal of tissue fibrosis, improvement of tissue fibrosis has been achieved and thereby the tissue function has been also improved [e.g. Diabetes, 45, 522-530, (1996), Proc. Natl. Acad. Sci. USA, 96, 12719-12724, (1999) and Proc. Natl. Acad. Sci. USA, 97, 8015-8020, (2000)]. It has been also known that by administering a compound which suppressively acts on intracellular signal transduction via TGF-β, improvement in fibrosis of a tissue has been achieved and thereby the tissue function has been also improved [e.g. Autoimmunity, 35, 277-282, (2002), J. Hepatol., 37, 331-339, (2002) and Life Sci., 71, 1559-1606, (2002)].
Thus, there is a need for development and provision of a drug which improves fibrosis of a tissue by decreasing expression of a Type I collagen gene in the tissue to reduce accumulation of collagen (i.e. a collagen accumulation-suppressing agent and a fibrosing disease-treating agent).